Mg2+-Dependent Modulation of BKCa Channels by Genistein in Rat Arteriolar Smooth Muscle Cells
Mg2+-Dependent Modulation of BKCa Channels by Genistein in Rat Arteriolar Smooth Muscle Cells
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金雀异黄素对大鼠小动脉平滑肌细胞中 BKCa 通道的 Mg2 依赖性调节
DOI：
10.1002/jcp.24648
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发表时间：
2014-12-01
影响因子：
5.6
通讯作者：
Yu, Guichun
中科院分区：
文献类型：
--
作者：
Wang, Xiaoran;Zhao, Tingting;Yu, Guichun
染料木黄酮是一种蛋白酪氨酸激酶（PTK）抑制剂，可调节离子通道活性。然而，染料木黄酮对大电导钙激活钾（BKCa）通道的作用机制尚不清楚。本研究旨在探讨镁离子依赖性调节血管平滑肌细胞BKCa通道活性的机制是否涉及染料木素抑制磷酸化或染料木素与BKCa通道之间的直接相互作用。采用全细胞膜片钳技术和内面向外膜片钳技术观察大鼠肠系膜小动脉平滑肌细胞BKCa通道电流及染料木素对BKCa通道活动的影响。我们发现染料木黄酮对BKCa电流的影响是Mg ~（2+）依赖性的。当细胞内游离镁浓度（[Mg ~（2+）]i）为2 M或20 M时，Genistein（50 M）抑制BKCa电流，而当[Mg ~（2+）]i为200 M或2000 M时，Genistein（50 M）放大BKCa电流。染料木素对BKCa电流的抑制作用可被蛋白酪氨酸磷酸酶抑制剂原钒酸钠（0.5mM）逆转。大豆黄酮（50 M），染料木素的一种无活性类似物，也放大BKCa电流，其放大对原钒酸不敏感。另一种PTK抑制剂tyrphostin 23（50 M）降低了BKCa通道的开放概率。这种抑制作用在200 M [Mg ~（2+）] i时比在2 M [Mg ~（2+）]i时弱，并且被原钒酸盐抵消。我们的研究结果表明，染料木黄酮在高[Mg ~（2+）]i时放大BKCa电流，但在低[Mg ~（2+）]i时抑制BKCa电流。这种双相效应的机制涉及PTK非依赖性扩增和[Mg 2 +]i-PTK依赖性抑制。J.细胞。229：1981-1989，2014。(c)2014年威利期刊公司
Genistein, a protein tyrosine kinase (PTK) inhibitor, regulates ion channel activities. However, the mechanism of action of genistein on large-conductance calcium-activated potassium (BKCa) channels is unclear. This study aimed to investigate whether the mechanism of Mg2+-dependent modulation of BKCa channel activity in vascular smooth muscle cells involved inhibition of phosphorylation by genistein or direct interaction between genistein and BKCa channels. The whole-cell and inside-out patch-clamp techniques were used to measure BKCa currents and the effects of genistein on BKCa channel activities in rat mesenteric arteriolar smooth muscle cells. We found that the effects of genistein on BKCa currents were Mg2+-dependent. Genistein (50M) inhibited BKCa currents if the intracellular free magnesium concentration ([Mg2+]i) was 2M or 20M, but amplified BKCa currents if [Mg2+]i was 200M or 2000M. The inhibitory effect of genistein on BKCa currents was reversed by the protein tyrosine phosphatase inhibitor sodium orthovanadate (0.5mM). Daidzein (50M), an inactive analogue of genistein, also amplified BKCa currents, and its amplification was insensitive to orthovanadate. Another PTK inhibitor, tyrphostin 23 (50M), reduced the open probability of BKCa channels. This inhibitory effect was weaker at 200M [Mg2+]i than at 2M [Mg2+]i, and was countered by orthovanadate. Our results suggest that genistein amplifies BKCa currents at a high [Mg2+]i, but inhibits BKCa currents at a low [Mg2+]i. The mechanism of this biphasic effects involves PTK-independent amplification and [Mg2+]i-PTK-dependent inhibition. J. Cell. Physiol. 229: 1981-1989, 2014. (c) 2014 Wiley Periodicals, Inc.